Adjustable machine reamer

ABSTRACT

An adjustable machine reamer in which a screw connection is provided between the expansion member and the reamer shank, a threaded projection or attachment arranged on an extension at the rear end of the expansion member and a tapped bore formed in the reamer shank and having an internal screw thread adapted to the external screw thread on the threaded projection on the expansion member. The extension at the rear end of the expansion member and the reamer shank each have one annular, face ground bearing face thereon for aligning the longitudinal axes of the expansion member and of the shank relatively to each other. There are also provided an axial centering means having a ground centering bore in the reamer shank and a centering cylinder fitting into the centering bore on the extension at the rear end of the expansion member.

United States Patent Merz 1 Feb. 8, 1972 [54] ADJUSTABLE MACHINE REAMERPrimary ExaminerFrancis S. Husar [72] Inventor: Adolf Merl, Olten,Switzerland Atmmey woodhams' Blanchard and Flynn [73] Assignee: Merz AGDulliken, Dulliken, Switzerland [57] ABSTRACT [22] Filed: Dec. 24, 1969An adjustable machine reamer in which a screw connection is [30] ForeignApplication Priority Data Dec. 27, 1968 Austria ..A 12 589/68 [52] US.Cl ..408/197 [51] Int. Cl ....B23d 77/04 [58] Field of Search ..77/76;408/197 [56] References Cited FOREIGN PATEN'IS OR APPLICATIONS 275,2088/1957 Switzerland ..77/76 provided between the expansion member and thereamer shank, a threaded projection or attachment arranged on anextension at the rear end of the expansion member and a tapped boreformed in the reamer shank and having an internal screw thread adaptedto the external screw thread on the threaded projection on the expansionmember. The extension at the rear end of the expansion member and thereamer shank each have one annular, face ground bearing face thereon foraligning the longitudinal axes of the expansion member and of the shankrelatively to each other. There are also provided an axial centeringmeans having a ground centering bore in the reamer shank and a centeringcylinder fitting into the centering bore on the extension at the rearend of the expansion member.

5 Claims, 3 Drawing Figures ADJUSTABLE MACHINE REAMER The inventionrelates to an adjustable machine reamer having a reamer shank and areplaceable reaming head which is of the sleeve-ring type, is endlesslycorrugated in cross section and has cutting edges arranged on shouldersformed by radial projections on the reaming head, the reaming head beingresiliently tensioned between an expansion member bearing against itsinterior and fast with the reamer shank and a sleeve arranged fordisplacement on the reamer shank and supported on a nut screwed on theshank, and being radially expansible by axial displacement relative tothe expansion member, being furthermore supported on the expansionmember only with a forward conical portion of its inner corrugationcrests.

A machine reamer of this kind is known from Swiss Pat. No. 275,208 andis there disclosed as two variants of embodiment (which are in principleequivalent) of adjustable machine reamers of the above-discussed type.The two variants differ, substantially, only in that the reaming head,in the case of a first variant, is arranged between a tapped expansionmember screwed on to a threaded pin at the forward end of the reamershank and a flange on the reamer shank, and, in the case of the secondvariant, between an expansion member constituting the forward end of thereamer shank and a flanged sleeve which is displaceable on the shank andsupported on a nut screwed on to the shank. In the case of the firstvariant, therefore, the rear side of the reaming head bears firmlyagainst a flange on the reamer shank and may be adjusted by screwing toa greater or lesser extent of the expansion member projecting from thefront into the head on to the threaded pin on the reamer shank. In thecase of the second variant, on the other hand, the reaming head bearsfirmly against the expansion member projecting into it from the frontand constituting the forward end of the reamer shank and may be adjustedby displacing a flanged sleeve bearing against its rear side or byrotating a nut forming the means of supporting the flanged sleeve andscrewed on to the shank. Since the reaming head, in the case of thefirst variant, bears, rearwardly, firmly against the reamer shank and,in the case of the second variant, bears forwardly firmly against thereamer shank or the expansion member constituting the forward endthereof, the reaming head may, when assembling the reamer, in the caseof the first variant be pushed from the front on to the reamer shank orthe threaded pin at the forward end of the reamer shank, whereas in thecase of the second variant the reaming head must, on assembling thereamer, be pushed from the rear over the entire shank, in which casesubsequently the flanged sleeve is pushed on and then the nut providedfor supporting the same is screwed on to the shank. From this it will beclear that the second variant is suitable, practically speaking, onlyfor embodiments of the machine reamer wherein the inner aperture widthof the sleeve-ringlike reaming head is larger than the largest diameterof the reamer shank in the zone between the rear end of the reamer shankand the expansion member arranged at its forward end, whereas, incontradistinction thereto, in the case of the first variant the onlyprecondition is that the outer diameter of the reaming head should belarger than the largest diameter of the reamer shank. Thus, the secondvariant was suitable only for relatively large reamer diameters whereasthe second variant required to be used with relatively small and mediumreamer diameters.

However, the first variant affords, as compared with the second variant,a lesser degree of accuracy with regard to the circular twist of thereaming head, due to the fact that an expansion member screwed on to athreaded pin does not, even if the threads of the tapped bore in theexpansion member and of the threaded pin on the reamer shank are ground,afford centering which is as satisfactory as that provided by anexpansion member connected in one piece with the reamer shank, inaccordance with the second variant, and since furthermore, in the caseof an expansion member screwed on to a threaded pin, there is apossibility that the longitudinal axis of the expansion member and thelongitudinal axis of the reamer shank or of the threaded pin on thereamer shank may not be accurately aligned relatively to each other, forexample because the distribution of the pressure points between theexternal screw thread in the expansion member and the external screwthread on the threaded pin is not entirely uniform in the peripheraldirection.

Within the framework of progressively increasing automation ofindustrial manufacture, however, there is a progressive increaseprecisely in respect of demands made with regard to the maximumpermissible circular twist in machine reamers, in particular also withinthe range of smaller and medium reamer diameters for which, hitherto(for the reasons mentioned hereinabove) only the first variant wassuitable. Now, it would theoretically be possible to satisfy theseincreased demands by going over to the second variant also within therange of relatively small and medium reamer diameters. This, however,would mean that it would be necessary to greatly diminish the shankdiameter so as to make the second variant possible also in the case ofsmall and medium reamer diameters. This, however, is opposed by thefactor that, first of all for strength and stability reasons andsecondly also due to the conversion involved thereby of the machineequipment of the industry to correspondingly smaller-dimensioned holdersfor the reamer shank, a diminution in this manner of the shank diametercould not be considered.

Thus, it was the problem on which the invention is based to provide anadjustable machine reamer which, on the one hand, has the advantages ofthe said second variant with regard to accurate centering and alignmentrelatively to each other of the longitudinal axis of the expansionmember and of the longitudinal axis of the reamer shank, and therewithof the extremely small circular twist achievable thereby and, on theother hand, however, does not, as in the case of the said secondvariant, require that the reaming head should be pushed on from the rearover the entire reamer shank or that the inner aperture width of thereaming head should be larger than the shank diameter at its largestpoint.

According to the invention, this is achieved with a machine reamer ofthe type mentioned at the outset, characterized by a screw connectionbetween the expansion member and the reamer shank, having a threadedprojection or attachment arranged on an extension at the rear end of theexpansion member and a tapped bore fonned in the reamer shank and havingan internal screw thread adapted to the external screw thread on thethreaded projection on the expansion member, there being in each caseone annular, face ground bearing face on the extension at the rear endof the expansion member and on the reamer shank, for alignment of thelongitudinal axes of the expansion member and of the shank relatively toeach other, an axial centering means having a ground centering bore inthe reamer shank and a centering cylinder fitting into the centeringbore on the extension at the rear end of the expansion member.

Advantageously, with this arrangement, the bearing face on the reamershank may be constituted by the forward end of the reamer shank and thebearing face on the extension or prolongation at the rear end of theexpansion member may be formed by a step on the said extension.

Furthermore, each of the two annular bearing faces may expediently bearranged in the zone of one end of the centering bore or of thecentering cylinder, so that at least the bearing face arranged in thezone of one end of the centering cylinder may be ground in the sameworking step with the grinding of the centering cylinder.

A preferred embodiment of the present machine reamer has a conicalexpansion member having a cylindrical projection or attachment forming afirst portion of the extension at the rear end of the expansion memberof smaller diameter than the inner aperture width of the reaming head, astep, constituting the annular bearing face on the extension, at therear end of the cylindrical projection, a second portion of theextension constituting the centering cylinder and adjacent the firstportion, an intermediate member adjacent the centering cylinder andhaving a diameter smaller than that of the centering cylinder, and anend member, constituting the threaded projection, of the extension, andalso an appropriate arrangement of the centering bore and of thethreaded bore in the reamer shank. Advantageously, with thisarrangement, in order to achieve maximum accuracy in the centering ofthe expansion body, the intermediate member and the centering cylindermay, together, be longer than the conical expansion body and thecylindrical projection.

The invention will now be discussed in greater detail with reference toan example of embodiment and with reference to the accompanying figures,wherein:

FIG. 1 shows an example of embodiment of a machine reamer according tothe invention;

FIG. 2 shows the individual elements of the machine reamer, illustratedin FIG. 1, before the assembly thereof;

FIG. 3 shows a front elevation of the reaming head of the machine reamershown in FIGS. 1 and 2.

The machine reamer shown in FIG. 1 consists, as FIG. 2 shows, of areamer shank I having a ground centering bore 2 and a tapped bore 3 andalso a face-ground annular bearing face 4 at its forward end, a nut 6which is adapted to be screwed on the external screw thread 5 on thereamer shank l, a sleeve 8 supported through the agency of its rear endon the nut 6 and adapted to be pushed on to the ground forward end 7 ofthe reamer shank l, the reaming head 9 and the expansion member 10provided with an extension at its rear end and having a cylindricalprojection 11, a centering cylinder 12, an intermcdiate member 13 and athreaded projection or attachment 14.

The expansion member 10 is provided at its front side with a hexagonalaperture 15 for tightening the screw connection between the expansionmember 10 and the reamer shank l. The cylindrical projection 1 l at therear end of the expansion member 10 is formed with a radial bore 16 intowhich is pushed a drive pin 17 serving for the purpose of establishing aconnection which is fast in rotation between the cylindrical projection11 or the expansion member 10, in one piece therewith, and the reaminghead 9, as will be apparent, in detail, from the front view of thereaming head shown in FIG. 3.

For the assembly of the reamer, first of all the nut 6 is screwed on tothe screw thread 5 and, subsequently, the sleeve 8 is pushed on to thefront end 7 of the reamer shank 1. Thereupon, the reaming head 9 ispushed on to the extension at the rear end of the expansion member 10until it is approximately within the zone of the cylindrical projectionl 1. Then, the section of the extension constituted by the threadedprojection 14, the intermediate member 13 and the centering cylinder 12is introduced, at the rear end of the expansion member 10, into the borein the reamer shank and the threaded projection 14 is screwed fast inthe tapped bore 3, until the annular bearing face 18 at the rear end ofthe cylindrical projection 11 bears firmly on the annular bearing face 4at the forward end of the reamer shank. When the annular bearing faces 4and 18 are located accurately in planes through which the longitudinalaxis of the reamer shank or of the expansion member extendsperpendicularly (or vertically) and the plane movement of the saidannular bearing faces is sufficiently small, the longitudinal axis ofthe expansion member is, due to the tightening action, alignedaccurately relatively to the longitudinal axis of the reamer shank.Furthermore, on such tightening taking place, the longitudinal axis ofthe expansion member is accurately centered relatively to thelongitudinal axis of the reamer shank by the centering cylinder 12 andthe centering bore 2, if the circular twists of the centering cylinder12 and of the centering bore 2 are negligibly small and the fit betweenthe centering cylinder 12 and the centering bore 2 is extremely close.

After the securing of the screw connection between the expansion member10 and the reamer shank 1, the nut is then screwed forwardly until theforward conical portion 19 of the inner corrugation crests 20 of thereaming head 9 bears on the expansion member 10 and (if appropriate) iswidened to the desired extent. For adjustment of the reamer, it is thenin every case necessary merely to so rotate the nut 6 that furtherwidening of the forward conical portion 19 of the inner corrugationcrests 20 of the reaming head 9, and therewith a correspondingenlargement of the outer diameter of the reaming head 9 at its forwardend, takes place.

In the constructional design of the present machine reamers, thefollowing points must be noted: first of all, care must be taken toensure that the annular bearing faces 4 and 18 are located as accuratelyas possible within planes through which the longitudinal axes of thereamer shank or of the expansion member extend perpendicularly orvertically, i.e., care is to be taken to ensure that, on grinding thesaid annular bearing faces, the rotations of the reamer shank or of theexpansion member take place exactly about the longitudinal axis thereofand that the grinding tool is guided exactly perpendicular to thepivoting axis. At the same time, as far as possible plane motion of thesaid annular bearing faces on rotation about the longitudinal axis ofthe reamer shank or of the expansion body is to be effected below 5;].and if possible even below 31.1.. Secondly, care is to be taken that thecircular twist of the centering cylinder 12, on rotation of theexpansion member 10 about its longitudinal axis and the circular twistof the centering bore 2 on rotation of the reamer shank about itslongitudinal axis, is to be as small as possible. It should expedientlybe below 10p. and if possible below 5p. To this end, during the grindingof the centering cylinder 12 and of the centering bore 2, care must betaken to ensure that the expansion member or the reamer shank arerotated with maximum accuracy about their longitudinal axis and that thegrinding tool is guided as far as possible exactly parallel to the pivotaxis. Furthermore, it must be ensured that the diameter of the centeringcylinder 12 and of the centering bore 2 expediently correspond exactlyto each other, at at least 10p. and if possible even at less than 5pThirdly, an intermediate member 13 will expediently be provided betweenthe centering cylinder 12 and the threaded projection 14, so that thecentering cylinder 12 and the intermediate member 13 are, together,longer than the expansion member 10 and the cylindrical projection 11.With this arrangement, the result may be achieved that nonuniformdistribution of the bearing points between the threaded projection 14and the threaded bore 3 along the periphery thereof is not able to exertany or any substantial negative influence on the centering and alignmentof the longitudinal axis of the expansion member relatively to thelongitudinal axis of the reamer shank. Furthermore, the intermediatemember 13 has the advantage that it may, by tightening the threadedprojection 14 in the threaded bore 3, be pretensioned to such an extentthat the force with which the two annular bearing faces 4 and 18 arepressed one upon the other or by means of which the expansion body 10 isretained is substantially larger than any forces which may becomeoperative on putting into use of the machine reamer in the direction ofan eccentric displacement of the expansion member 10, thereby renderingsuch forces ineffective. Fourthly, the circular twist of the front end 7of the reamer shank, on to which the sleeve 8 is pushed on, andfurthermore also the circular twist of the bore in the sleeve 8 is to bekept as low as it possibly can be, expediently below 1011 and the fitbetween this forward end 7 and the bore in the sleeve 8 is to be asclose as possible. Furthermore, the length of the sleeve 8 is to be madeas large as possible. Due to this fit of maximum closeness between thesleeve 8 and the cylindrical end 7 and the greatest possible length ofthe sleeve 8, the result is achieved that the longitudinal axis of thereaming head 9, the rear end of which bears on the front side of thesleeve 8, is aligned exactly relatively to the longitudinal axis of thereamer shank. The centering of the reaming head 9 is then effected bymeans of the expansion member 10. In order to achieve maximum accuracyin the alignment of the axis of the reaming head 9 on the longitudinalaxis of the reamer shank 1, furthermore, the rear side of the reaminghead and at least the front side of the sleeve 8 should be face-ground.

Using machine reamers according to the invention, with unvaried shankdimensions, it is possible, also within the range of small and mediumreamer diameters, to achieve circular twist of the reaming head lessthan p, this being something which hitherto had been impossible withinthese diameter ranges.

lclaim:

1. Adjustable machine reamer having a reamer shank and having areplaceable reaming head having the shape of a sleeve ring and which, incross section, is endlessly corrugated and which has cutting edgesarranged on shoulders formed by radial projections on the reaming head,the reaming head being resiliently tensioned, between an expansionmember bearing against its interior and fast with the reamer shank and asleeve arranged for displacement on the reamer shank and supported on anut screwed on to the shank, about the expansion member and radiallyextensible by axial displacement relatively to the expansion member andfurthermore supported on the expansion member only through the agency ofa forward, conical portion of its inner corrugation crests,characterized by a screw connection between the expansion member and thereamer shank and including a threaded projection arranged on anextension at the rear end of the expansion member and a tapped boreformed in the reamer shank and having an internal screw threadcorresponding to the external screw thread on the threaded projection ofthe expan sion member, an annular face-ground bearing face on theextension at the rear end of the expansion member and on the reamershank for alignment of the longitudinal axes of the expansion member andthe shank relatively to each other, and an axial centering means havinga ground centering bore in the reamer shank and a centering cylinder onthe extension at the rear end of the expansion member and fitting intothe centering bore.

2. Machine reamer according to claim I, characterized in that thebearing face on the reamer shank is formed by the front end of thereamer shank and the bearing face on the extension at the rear end ofthe expansion member is formed by a step on the said extension.

3. Machine reamer according to claim 1, characterized in that each ofthe two annular bearing faces is arranged in the zone of one end of thecentering bore and of the centering cylinder.

4. Machine reamer according to claim 1 characterized in that the conicalexpansion member has a projection forming a first portion of theextension and located at the rear end of the expansion member, the saidprojection having a smaller diameter than the inner aperture width inthe reaming head a step constituting the annular bearing face on theextension at the rear end of the cylindrical projection, a secondportion of the extension constituting the centering cylinder anddisposed I adjacent the first portion, an intermediate member adjacentthe centering cylinder having a smaller diameter than that of thecentering cylinder, and an end member of the extension constituting thethreaded projection.

5. Machine reamer according to claim 4, characterized in that theintermediate member and the centering cylinder are, together, longerthan the conical extension member and the cylindrical projection.

1. Adjustable machine reamer having a reamer shank and having areplaceable reaming head having the shape of a sleeve ring and which, incross section, is endlessly corrugated and which has cutting edgesarranged on shoulders formed by radial projections on the reaming head,the reaming head being resiliently tensioned, between an expansionmember bearing against its interior and fast with the reamer shank and asleeve arranged for displacement on the reamer shank and supported on anut screwed on to the shank, about the expansion member and radiallyextensible by axial displacement relatively to the expansion member andfurthermore supported on the expansion member only through the agency ofa forward, conical portion of its inner corrugation crests,characterized by a screw connection between the expansion member and thereamer shank and including a threaded projection arranged on anextension at the rear end of the expansion member and a tapped boreformed in the reamer shank and having an internal screw threadcorresponding to the external screw thread on the threaded projection ofthe expansion member, an annular face-ground bearing face on theextension at the rear end of the expansion member and on the reamershank for alignment of the longitudinal axes of the expansion member andthe shank relativelY to each other, and an axial centering means havinga ground centering bore in the reamer shank and a centering cylinder onthe extension at the rear end of the expansion member and fitting intothe centering bore.
 2. Machine reamer according to claim 1,characterized in that the bearing face on the reamer shank is formed bythe front end of the reamer shank and the bearing face on the extensionat the rear end of the expansion member is formed by a step on the saidextension.
 3. Machine reamer according to claim 1, characterized in thateach of the two annular bearing faces is arranged in the zone of one endof the centering bore and of the centering cylinder.
 4. Machine reameraccording to claim 1 characterized in that the conical expansion memberhas a projection forming a first portion of the extension and located atthe rear end of the expansion member, the said projection having asmaller diameter than the inner aperture width in the reaming head astep constituting the annular bearing face on the extension at the rearend of the cylindrical projection, a second portion of the extensionconstituting the centering cylinder and disposed adjacent the firstportion, an intermediate member adjacent the centering cylinder having asmaller diameter than that of the centering cylinder, and an end memberof the extension constituting the threaded projection.
 5. Machine reameraccording to claim 4, characterized in that the intermediate member andthe centering cylinder are, together, longer than the conical extensionmember and the cylindrical projection.